Some of the energy generated by the engine is used to drive various items of equipment thereof. The power required is taken off mechanically, generally on the shaft of the high-pressure body of the gas turbine engine, by a take-off shaft that is connected to the shank of the input pinion in the accessory gearbox. The gearbox is mounted on the casing of the engine and contains a certain number of items of equipment or accessories that it supports, for example an electricity generator, an alternator, hydraulic fuel and oil pumps, a starter, etc.
The gearbox comprises an elongate housing inside which gear wheels are mounted forming a gear train driving the equipment. These gears comprise a shank that can be connected to the drive shaft of an item of equipment. One of the gears is also connected to the input shaft of the gearbox. The various apparatuses driven by the gearbox are mounted directly on the housing, and the associated drives pass through the wall of the housing through suitable openings. The gears forming the gear train inside the housing generally have axes parallel to one another. According to the known prior art of the present applicant, the shanks of the pinions are supported firstly by the wall of the housing that is opposite that which comprises the opening through which the equipment is driven, and secondly by the wall comprising the opening or a cover attached to the wall. As a general rule, the shank of the pinions of the gear wheel is carried firstly by the outer race of a rolling or ball bearing fixed to the imperforate bottom wall of the housing and secondly by the outer race of a ball or roller bearing fixed to the cover associated with the accessory. The gear wheel for its part is situated between the two bearings.
The present applicant has already proposed improvements relating to this type of accessory gearbox, described for example in the applications WO 2012/175884 or EP 1.898.072.
Such an arrangement needs a certain amount of space in the direction of the axes of the gears. In the context of the continuous improvement of its products, the present applicant wishes to reduce the space requirement in this direction. It should be noted that roller bearings have a capacity for misalignment that requires a minimum space between axes, and this space between axes limits the possibility of reducing the thickness of the gearboxes. Unless the capacities for misalignment of the rollers are increased and therefore their load capacity reduced, a different solution for assembly must be found.